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Patented Oct. 28, 1947 ALLOY STEEL Janet Z. Briggs, New York, -N. Y., 'assignor to Crucible Steel Company of America, New York, N. Y., a corporation of New Jersey No Drawing. Application July 22, 1943, Serial No. 495,759

This invention pertains to an alloy steel, of relatively low total alloy content, and possessing the .properties of high strength and high resistance to corrosive gases at elevated temperatures, to-

gether with good forgeability and machineability.

The steel of the invention is well adapted, among other applications, for use in airplane turbo-superchargers, especially for the rotary elements thereof exposed to the high temperature gases, including the wheel or bucket carrying discs employed in certain constructions. Such superchargers are driven by the hot exhaust gases discharged from the motor. The rotary or turbo unit of the supercharger is thus exposed to highly corrosive gases at high temperatures of the order of 1200 to 1500 F. and upwards.

A steel to be suitable for purposes aforesaid must have sufficiently high strength at the temperatures encountered to resist deformation and yielding under impact of the hot gases and resulting stresses set up therein; and must also have sufficiently highv resistance to the high temperature corrosive gases to which it is subjected, that it will not be appreciably corroded or eroded by the same. At the same time, and for purposes of ease in fabrication, the steel must have good forgeability and machineability. Also, in conse- 4 Claims. (01. 7 -128) quence of the present emergency and scarcity of steel alloying elements, it is of vital importance that the steel possess all of the above characteristics, and at the same time employ a relatively low total alloy content.

Heretofore various relatively high alloy steels have been employed for this purpose, but none has proved entirely satisfactory by reason of such factors as: excessively high content of strategic alloys employed, or inadequate strength and corrosion resistance to the hot gases at the temperatures encountered, or difiiculties in forging and machining, or various combinations of these and related factors.

In accordance with the present invention, I have successfully overcome the above mentioned difiiculties by employing for purposes aforesaid, a relatively low alloy steel containing about: 15% to 25% chromium, 2% to 8% nickel, 2.5% to 8% manganese, at least 1 to about 10% of metal of the group consisting of molybdenum and tungsten, about 0.2% to 1.5% carbon, with optional additions up to about 5% columbium, silicon in usual amounts and preferably under 2 with the balance substantially iron. Such elements as nitrogen, phosphorus, sulfur, etc., are held within the usual tolerances. The steel of the invention is predominantly austenitic.

A preferred range of analysis in accordance A with the invention is about as follows: 0.3% to 0.5% carbon, 3.5 to 6% manganese, 1% silicon maximum, 16 to'19% chromium, 4% to 6% nickel, 1% to 2% molybdenum, 1% to 2% tungsten, and 1% columbium maximum, balance'substantially iron.

The following are some typical examples of steels in accordance with the invention which have given excellent results:

%C %Mn %Si %Cr %Ni %Mo %W %Cb Where the herein described and, claimed alloy steels are referred to as being forgeable or machineable, or as having high strength at elevated temperatures, or high resistance to corrosive gases at elevated temperatures, the above terms should be understood as meaning that said steels measure up to current commercial requirements in respect to such characteristics, for the uses and purposes above mentioned.

In the appended claims, by balance substantially iron is meant iron except for impurities Within usual commercial tolerances.

What I claim is:

1. A forgeable and machineable alloy steel, characterized by high strength and corrosion resistance at elevated temperatures, said steel containing a plurality of alloying elements, of which the following in the proportion stated are the only elements necessary to attain said characteristics: chromium 15 to 25%; nickel 2 to 8%; manganese 2.5 to 8%; metal of the group molybdenum and tungsten 1 to 10%; carbon over 0.2 to 1.5%; balance substantially all iron; said elements being present in relative proportions such as to render said steel predominantly austenitic.

2. A forgeable and machineable alloy steel, characterized by high strength and corrosion resistance at elevated temperatures, said steel containing a plurality of alloying elements, of which the following in the proportions stated are the only elements necessary to attain said characteristics: chromium 15 to 25%; nickel 2 to 8%; manganese 2.5 to 8%; metal of the group molybdenum and tungsten 1 to 10%; carbon over 0.2 to 1.5%; silicon under 1%; columbium under 1%; balance substantially iron; said elements being 3 present in relative proportions such as to render said steel predominantly austenitic.

3. A forgeable and machineable alloy steel, characterized by high strength and corrosion resistance at elevated temperatures, said steel containing a plurality of alloying elements, of which the following in the proportions stated are the only elements necessary to attain said characteristics: chromium 16 to 19%; nickel 4 to 6%; manganese 3.5 to 6% metal of the group molyb denum and tungsten 2 to 4%; carbon 0.3 to 0.5%; silicon under 1%; columbium under 1%; balance substantially all iron; said elements being present in relative proportions such as to render said steel predominantly austenitic.

4. A forgeable and machineable alloy steel,

characterized by high strength and corrosion resistance at elevated temperatures, said steel containing a plurality of alloying elements, of which the following in the proportions stated are the only elements necessary to attain said characteristics: chromium 16 to 19%; nickel 4 to 6%; manganese 3.5 to 6%; molybdenum 1 to 2%; tungsten 1 to 2%; carbon 0.3 to 0.5%; silicon under 1%; columbium under 1%; balance substantially all iron; said elements being present 4 in relative proportions such as to render said steel predominantly austenitic.

JANET Z. BRIGGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Alloys of Iron and Chromium, Kinzel and Franks, vol, II, High Chromium, pages 416, 417

5 and 418. Published by McGraw-Hill Book Co. of

New York, 1940. 

